Uterine fibroids (leiomyomata) are noncancerous growths that develop in or just outside a woman’s uterus (womb). Uterine fibroids develop from normal uterus muscle cells that start growing abnormally. As the cells grow, they form a benign tumor.
Who Gets Uterine Fibroids?
Uterine fibroids are extremely common. In fact, many women have uterine fibroids at some point in life. Uterine fibroids in most women are usually too small to cause any problems, or even be noticed.
No one knows what causes uterine fibroids, but their growth seems to depend on estrogen, the female hormone. Uterine fibroids don’t develop until after puberty, and usually after age 30. Uterine fibroids tend to shrink or disappear after menopause, when estrogen levels fall.
African-American women tend to get uterine fibroids two to three times as often as white women, and also tend to have more symptoms from uterine fibroids.
Other factors may influence development of uterine fibroids:
- Pregnancy: Women who have had children are less likely to get fibroids.
- Early menstruation: Women whose first period was before age 10 are more likely to have uterine fibroids.
- Women taking birth control pills are less likely to develop significant uterine fibroids.
- Family history: Women whose mothers and sisters have uterine fibroids are more likely to have them.
Types of Uterine Fibroids
All uterine fibroids are similar in their makeup: All are made of abnormal uterine muscle cells growing in a tight bundle or mass.
Uterine fibroids are sometimes classified by where they grow in the uterus:
- Myometrial (intramural) fibroids are in the muscular wall of the uterus.
- Submucosal fibroids grow just under the interior surface of the uterus, and may protrude into the uterus.
- Subserosal fibroids grow on the outside wall of the uterus.
- Pedunculated fibroids usually grow outside of the uterus, attached to the uterus by a base or stalk.
Uterine fibroids can range in size, from microscopic to several inches across and weighing tens of pounds.
Symptoms of Uterine Fibroids
Most often, uterine fibroids cause no symptoms at all -- so most women don’t realize they have them. When women do experience symptoms from uterine fibroids, they can include:
- Prolonged menstrual periods (7 days or longer)
- Heavy bleeding during periods
- Bloating or fullness in the belly or pelvis
- Pain in the lower belly or pelvis
- Pain with intercourse
Some experts believe that some uterine fibroids can occasionally interfere with fertility and pregnancy. Although it's rare, a uterine fibroid projecting into the uterus might either block an embryo from implanting there, or cause problems with the pregnancy later.